On page 29 it says "The leaves of a parse tree read from left to right form the yield of the tree, which is the string generated or derived from the nonterminal at the root of the parse tree. In Fig. 2.2 the generated string is 9-5*2. In that figure, all the leaves are shown at the bottom level. Henceforth, we shall not necessarily line up the leaves in this way." why not?
It also says "Any tree imparts a natural left-to-right order to its leaves, based on the idea that if a and b are two children with the same parent, and a is to the left of b, then all descendants of a are to the left of descendants of b." what does it mean?
P.S It's the second edition of the book
So first of all, for anyone else wanting to comment on this, the page numbers above refer to the first edition. In the second edition, the page number is 46, and the diagram referred to is figure 2.5.
EDIT: The author, when referring to extending the leaves down to the bottom, is talking about moving all leaves of the tree to be aligned vertically with each other, whether or not they are at the same level in the tree. Figure 2.2 has them extended to the bottom, such that every leaf is at the bottom of the diagram, aligned together vertically from left to right. If you look at some of the other diagrams later in the book, this is not done, and leaves are shown vertically aligned with other nodes at the same level, whether or not those other nodes are leaves. This latter way is the normal way of drawing trees, and is the most space efficient.
As for your first question, I believe the reason they do not do that is to save room. If you look at the right hand side of figure 2.4, if the author was to extend the leaves down to the bottom, then the subtree with letter as its root would have to be moved to the right, taking up more room than what is actually needed. While this is a minimal case and doesn't make a huge difference, one could imagine a larger tree (which I'm sure is in the book, although I didn't go looking) which would need more room.
For the second question, it is essentially saying that if you had a*b + c*d, and you considered the multiplications as siblings (as they would be to keep order of operations valid), then the leaves a and b would be to the left of c and d in the tree, just as they are to the left of c and d in the equation. Essentially its just saying what it already said in the first part, which is that the tree's leaves should be able to be read left to right in order to reproduce the original syntax exactly, not switching the ordering of any portions (i.e. if the tree read left to right c*d + a*b, that might still be valid, but would not be a tree we are considering).
Related
For the context, I'm working with Capella, an Eclipse RCP application based on Sirius (hence, EMF, GMF and draw2d). This application is used for MBSE, that basically means diagram representations for industrial systems.
I'm developping an add-on (viewpoint) to display custom labels next to diagram elements. These diagram elements are, to put it simply, boxes inside boxes. My problem is that usually the label text is larger than the space between a box and its container, so the label gets hidden. What I need is these labels to always be in foreground. As I'm more used to web development, what I'm looking for would be the equivalent of the z-index CSS property.
Currently I have no idea of how to achieve this, I'm using a custom .odesign that allows me to control some rendering options, like labels text, the color of some elements or to add decoration, but I dont think its the way to go for my problem. Maybe I should use a custom EditPart or a custom StyleConfiguration (I already used these components for other projects) but I have no clue where to start for this issue.
Any leads will be greatly appreciated.
We recently did this kind of changes to keep some labels in Sirius Sequence diagrams always on top: the combined fragments are placed behind the lifelines (z order) but we wanted to keep the labels of the CombinedFragments visible event their bounds intersects Lifelines, Executions or States).
This has been handled in Bug 564239 for Sirius 6.3.2 (used in Capella 1.4.1).
You could find some hints the bugzilla (Gerrits and commits can be retrieved from the See also section).
In Sirius Sequence diagram , we use org.eclipse.sirius.diagram.sequence.ui.tool.internal.layout.SequenceZOrderingRefresher to control the z-order of CombinedFragments : all the figures that composes them comes from some expressions in the odesign, and synchronization with the Capella model for exemple.
But in your case you want to control only the label, so it must not be dealt on the edit par level, but on the figure one. The "overlay" layer and figure lead might be a good one.
Do not forget another thing: in GMF/GEF, the labels of an element is displayed/shown/rendered/visible if it fits to the visible area of the parent container: in the case of a node in a container with scrollbar, the visible are will impact the visibility of the sub nodes (extended to their border nodes, edges, labels, ...)
Regards
Maxime
Is there an optimal layout in JUNG for left-to-right placement of nodes in the graph? I'm looking for something that would model a data lineage and need to represent this somewhat linearly (left to right).
If your graph is a tree, then you can use the TreeLayout and do some post-processing to rotate it to have the root on the left instead of the top (see the L2RTreeLayoutDemo for an example of how to do this).
If your graph is only sort of tree-shaped, then you may want to extract a tree from your graph first (see MinimumSpanningTreeDemo for one way to do this automatically) and then follow the procedure above.
If neither of those works for you (for example, this won't work if your graph has multiple "roots"), then you will probably need to create your own layout, perhaps based on TreeLayout.
I'm building a color box connecting game with objective-C and trying to figure out how to find the correct position when a block of boxes is placed incorrectly over another block of boxes.
See the attach image. In the image, you only need to move the left box one step to the right in order to connect the boxes and win.
However, if you place the left box on top of the other box (Image 2), I want to move it to the closest available free grid position.
This would be easy if the box was a simple square (a 1x1 grid, 2x2 grid, etc), but since the boxes can be complex, It's harder. There might also be a lot of boxes on the grid.
Any suggestions would be very appreciated.
If you're new to heuristics like this, just take the KISS approach.
It couldn't be easier...
The user tries the object at x,y ok?
It does not "fit" there.
So, simply "spiral" outwards, trying it in other possible places.
Just keep trying until you find one where it fits.
234
915
876
so that's like "radius 1", you see? then try "radius 2"
and so on.
It's that easy. Just keep trying until you find one that "does work".
Work from the start position outwards, so that, you find the closest one.
I am a beginner at ActionScript3, and for my learning purpose, I am trying to build a match3 kind of game. I am making is a clone of bejeweled kind of game. but instead of swapping, I have to delete those elements and shift the upper elements down and add new elements above those shifted elements.
I am able to delete matched elements and after matching I'm removing those elements but I am stuck with the shifting code. I am not able to shift those elements down.
I believe that you should take a look at Richard Lord's Tetris source code as your game may be somehow similar in mechanics to Tetris. Tetris shifts down rows when you get lucky.
Richard Lord is one of the Flash Gurus and his way of doing things may seem pretty advanced for a starter like you. Take a look over the source code and see if it fits you. What I can tell is that this is the proper way to make a game but maybe it's not the best point to start for a novice like you that is in urgent need.
http://www.richardlord.net/blog/actionscript-3-tetris-source-code
I would approach it like this in 2 parts.
Loop through your array of board positions starting from the bottom row and check for an empty unoccupied slot, if you find one do another loop through the row above till you find a piece on the same column. If you find a piece on the row above apply a tween to move it down to the empty slot and continue your loop.
Once you have looped through all rows, and animated all the tweens you need to loop through again to find all the gaps that need gems dropped into them. Create new elements at those positions and then move them up by (element height * row), apply another tween to animate them back to their starting position.
I have a two-column paper where space restrictions are very tight.
I just looked at my last version of the manuscript and saw that the upper half contains a figure (as expected), but in the lower half there is a lot of vertical space between paragraphs (enough to squeeze 10 more lines), and that LaTeX probably added it so that in the beginning of the next page a new numbered section will begin at the top of the page.
I know there's a way to adjust this so LaTeX doesn't try so hard, but I'm not sure how. any help? Thanks!
The parameter that controls inter-paragraph spacing is called \parskip(See Paragraph Spacing ). You set it (with "rubber" values) using something like:
\setlength{\parskip}{1cm plus4mm minus3mm}
The defualt value of \parskip is class dependent. The "plus" and "minus" parts tell TeX how much it can adjust the value to improve the layout (that is they make the spacing elastic, thus the "rubber" designation). Reducing (or eliminating) the "plus" part of the rubber might help.
Watch out though, you can cause other layout artifacts if you constrain TeX too much.
Other things to think about:
The widow and club penalties probably apply section headings, and may be affecting TeX's layout choices (see https://stackoverflow.com/questions/512967/how-can-one-keep-a-section-from-being-at-the-end-of-a-page-in-latex for a discussion).
You may also want to consider messing with \baselineskip which controls the allowed spacing between lines of text and can also have rubber values.
This is a common problem, and there are probably some fairly sophisticated treatments already prepared on CTAN.
\vfill before the new section worked perfectly for me.